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I I I I I I I I I I I I I I I I I I I I Monthlv Water Diversion and Unused Water in Leroux Creek System Actual diversion records and gauge data downstream of the Leroux Creek system show that there is unused water flowing into the North Fork of the Gunnison River. This availability results from the fact that some water holders are not using their water rights or do not have the capacity to use them during periods of high flows. The total irrigated area in the system is about 7,250 acres planted with pasture and alfalfa crops. Consumptive use for these crops was estimated at 1.68 acre-feet per year in previous studies (USBR, 1973). Thus, assuming a 37 percent system efficiency, total annual irrigation demands are about 33,000 acre-feet. Actual diversion records show excess water in the system since the mean flow is 38,739 acre-feet. Monthly diversion rates for the ditches in Leroux Creek were obtained from Colorado's on-line Decision Support Systems (http://cdss.state.co.us/cgi binlcgirun.exe) and are included in Appendix B. These diversions were tabulated and added to each other to estimate total diversions from the Leroux Creek. Arlalyzing the d~ta for diversions from the above ditches and discussing the issue with the Water Commissioner for Leroux Creek (Appendix A), the following assumptions were considered: 1. According to the Water Commissioner Jessie, Duke and Enos Hotchkiss ditches do not call for water from Leroux Creek. These ditches obtain water from return flows below Leroux Creek ditch and from local sources such as springs and runoff from the nearby hills. Therefore, diversions of the Jessie, Duke and Enos Hotchkiss were not included in our analysis of the diversion records. It should be noted that these ditches can exercise their decrees at anytime if needed. 2. Cow Creek is a tributary to Leroux Creek and it supplies the system with additional water not included in the readings of gauge 1345. To account for Cow Creek flows, an additional flow proportional to one half of Cow Creek's basin area is added to Leroux Creek inflows. The basin of Cow Creek is approximately 1,100 feet lower than the basin of Leroux Creek and was estimated at 16 percent ofthe area of Leroux above gauge 1345. Therefore to account for the difference in elevation, additional flows from Cow Creek were assumed to be 8 percent of Leroux Creek inflows. 3. Farmers use surface irrigation within the Leroux Creek system. They irrigate pasture and alfalfa, which results in high rates of return flows in the form of surface runoff. Analyzing the topography of the area it was found that: . Runoff from Overland, Stull, Current Creek, Highline and Midkiff & Arnold ditches most likely do not return to the system. Therefore, return flow from these ditches was disregarded. :J:~ -14-